More than 70% of voters favor banning or heavily regulating chemical injections into the ground to tap oil and natural gas, a USC Dornsife/L.A. Times poll finds.

As energy companies seek to plumb vast reserves of underground oil in California through the controversial drilling technique known as fracking, voters are concerned about its safety and uneasy with the state's lack of oversight, according to a new poll.

More than half of voters — 58% — say they favor a moratorium on the process of injecting chemicals deep into the ground to tap oil and natural gas deposits embedded in rock until an independent commission has studied its environmental effects. More than seven in 10 say they either want the process banned outright or more heavily regulated, according to the poll by the USC Dornsife College of Letters, Arts and Sciences and the Los Angeles Times.

Voters' concern about the environmental and safety implications of fracking, also known as hydraulic fracturing, surfaced repeatedly. Almost three in five voters said fracking should be prohibited in areas immediately surrounding sources of groundwater. And by a 15-point margin, a majority of voters backed tax incentives for companies with a record of operating safely.

Despite California's reputation as a trendsetter in environmental protection, it lags behind other parts of the country in the extent to which it has demanded oversight of the drilling method. Energy firms are permitted to keep secret the mix of chemicals they use to extract the oil and gas, the state is not given explicit notice of when and where fracking is taking place, and the rules in place to protect groundwater are not as strict as in some other states.

California's unique geography, however, positions the state for a fracking boom. One of the world's largest deep-shale oil reserves, accounting for roughly two-thirds of such oil reachable by fracking nationwide, runs mostly underground through a swath of the state from Modesto to south of Bakersfield. In March, USC released a study, funded in part by a grant from the Western States Petroleum Assn., concluding that a full expansion of fracking would generate hundreds of thousands of jobs and billions of dollars in new tax revenue.

Yet although energy firms have resisted tighter regulation, the poll findings suggest that more government oversight may be the path to public acceptance. Lawmakers have proposed several measures that would bring more government scrutiny to the process, as well as put a stop to it altogether until it can be studied further.

"Voters are suspicious of fracking," said Dan Schnur, director of the Jesse M. Unruh Institute of Politics at USC. He said Californians want energy companies "to abide by stricter regulations."

Nathan Hayes, 31, an unemployed Grass Valley resident, said he made up his mind that fracking was unsafe when he saw a YouTube video that activists had posted showing someone lighting his tap water on fire, blaming fracking nearby for the problem.

"Look up flammable water on YouTube and you will find it," he said. "It doesn't seem like these companies are willing to take responsibility for what they are doing to the planet. There should at least be studies. And the companies doing the fracking should be paying for them."

The prospect of more intense drilling in seismically sensitive areas also has put some Californians on edge. Among them is Alicia Hernandez, 68, a retired university clerk in Goleta.

"I think it is dangerous," she said. "We just had an earthquake. I am very, very concerned about drilling that deep. I just won't be comfortable with it no matter what."

Oil industry officials say that such concerns are rooted in fearmongering by environmentalists, and that scientific studies have shown the process of fracking, which has been used in California for decades, to be safe. Grant Bullock, 57, of Rancho Cordova says he sees no reason to doubt such assertions.

"The idea that people are going to be poisoned or oil companies don't care is a lot of bull," he said. "By law and by contract, they take care of a problem, if one should arise."

Bullock, an out-of-work information technology expert with three advanced degrees, said he spends his weekends collecting cans at music festivals for money — and he is frustrated that environmental activists may undermine the creation of sorely need jobs.

The poll results suggest that views on fracking in many cases flowed from existing concerns about the environment.

Among Latinos, a group of voters traditionally worried about the environment, 55% favored an immediate and outright ban on fracking that could be lifted only by the Legislature — a view shared by only 42% of whites. Sixty-four percent of Latinos sanctioned a moratorium that could be lifted only after an environmental study; a lesser 56% of whites shared that view.